1. Field of the Invention
The present invention relates to a non-contact type electric power supplying system for supplying electric power to a vehicle on a non-contact basis.
2. Description of the Related Art
Electrically powered vehicles, such as transportation means such as electric train carriages and monorails, and self-guided vehicles that carry parts in factories, and so forth are known. As one of means for supplying electric power to such electrically powered vehicles, a charging station system has been implemented. In the charging station system, however, whenever the electric power of the battery of the vehicle begins to run out, the user thereof should drive the vehicle to a charging station and charge it with electric power. Thus, when a parts conveying system in a factory is operated using such a charging system, the operating efficiency is low. Thus, when an electrically powered vehicle travels only over a predetermined route, a more effective system is required. To solve this problem, an electric power supplying system is used.
In the electric power supplying system, as in electric trains and monorails, a contact-type of electric power supplying system has been widely implemented. However, in this system, since the contact portions get worn, they should be maintained and periodically replaced with new ones. Moreover, in the contact-type electric power supplying system, since the contact portions are subject to sparking, such a system cannot be used in an explosion-protected area.
To solve such problems, non-contact type electric power supplying systems have been developed and implemented. Next, a non-contact type electric power supplying system will be described with reference to FIGS. 1 and 2.
FIG. 1 shows a conveying system using a system for supplying electric power from a feeder on a non-contact basis. In FIG. 1, a guide rail 12 is disposed on a route of a vehicle 13 as an example of the vehicle (denoted by dashed lines). A feeder 5 is disposed along the guide rail 12. The feeder 5 is composed by coating a conductor wire such as a copper wire with an insulation material. The feeder 5 is routed from a start point X of the guide rail 12 to an end point Y thereof. AC current is supplied from an AC power supply 11 to the feeder 5. The vehicle 13 has an electric power receiving unit 2 that receives electric power from the feeders on a non-contact basis. With the electric power received by the electric power receiving unit 2, the vehicle 13 travels from the start point X to the end point Y of the guide rail 12.
FIG. 2 is a partial sectional view showing the conveying system shown in FIG. 1. FIG. 2 shows principal portions including the electric power receiving unit 2 and the feeder 5 for explaining an electric power supplying method.
The guide rail 12 has a guide portion 15 that guides the vehicle 13. In addition, the electric power receiving unit 2 has guide rollers 14 that clamp the guide portion 15 of the guide rail 12. When the vehicle 13 travels, the guide rollers 14 rotate. In other words, the vehicle 13 travels along the guide rail 12.
The guide rail 12 has an outbound portion and a inbound portion of the feeder 5. The feeder 5 is held by support members 6 secured to the guide rail 12. As shown in FIG. 1, the feeder 5 supplies current from the AC power supply 11 so that the current is returned at the end point Y. In FIG. 2, the directions of the currents that flow in the outbound portion and the inbound portion of the feeder 5 are always reverse.
The electric power receiving unit 2 has an E-shaped magnetic material core 3. The E-shaped magnetic material core 3 is made of, for example, silicon steel or ferrite and formed in the shape of the letter E. The E-shaped magnetic material core 3 has a secondary coil 4 on the center protrusion portion thereof.
When the vehicle 13 is placed on the guide rail 12, the outbound portion and the inbound portion of the feeder 5 are placed in respective groove portions of the E-shaped magnetic material core 3. In this state, when an AC current is supplied to the feeder 5, the AC current causes an Alternating magnetic field to be generated. The Alternating magnetic field penetrates the E-shaped magnetic material core 3. Thus, due to the electromagnetic induction, the alternating magnetic field causes the secondary coil 4 to generate electromotive force. The electric power generated in the secondary coil is supplied to the vehicle 13. When the vehicle 13 travels, the guide rollers 14 or tires (not shown) provided for the vehicle 13 are rotated by the electric power. As described above, the electric power is supplied from the feeder 5 to the vehicle 13 on a non-contact basis.
In the non-contact type electric power supplying system using such electromagnetic induction effect, the supplying efficiency is an important factor. Next, with reference to FIG. 3, a problem about the supplying efficiency will be described.
In FIG. 3, a structural member 1 accords with the guide rail 12 shown in FIG. 2. The structural member 1 is made of aluminum, iron, or the like.
When the directions of the AC currents that flow in the outbound portion and the inbound portion (hereinafter, referred to as feeder 5-1 and feeder 5-2, respectively) are as shown in FIG. 3, the orientations of the magnetic fluxes thereof are denoted by arrows shown in FIG. 3. In other words, magnetic fluxes that flow around the feeders 5-1 and 5-2 are generated in the reverse directions. At this point, the magnetic flux generated by the feeder 5-1 penetrates the inside of the E-shaped magnetic material core 3 and travels from an edge portion A of the center protrusion portion of the E-shaped magnetic material core 3 to an edge portion B of an end protrusion portion thereof.
Part of the magnetic flux emitted from the edge portion A reaches the structural member 1. Thus, an eddy current that cancels the magnetic flux is generated in the structural member 1. Since part of the electric power supplied from the feeder 5 is consumed as heat by the eddy current, the electric power that is available on the secondary side (the electric power receiving unit 2) is decreased.
To solve such a problem, a technology disclosed in, for example, Japanese Patent Laid-Open Publication No. 6-30503, is known. (Hereinafter, the disclosed technology is referred to as the related art reference.) In the related art reference, a paramagnetic amorphous member (30) is disposed in a bracket (32) secured to a guide rail (the guide rail corresponds to the structural member 1 shown in FIG. 3) so as to decrease the eddy current that flows in the guide rail. However, since an eddy current is generated in the paramagnetic amorphous member because the electric resistance thereof is low, electric power is still consumed by the eddy current.